This invention relates to a robotic floor cleaning device and to a method of operating such a device.
Vacuum cleaners operate by having a fan unit which draws dirt-laden air through a dirty air inlet and then through a separating arrangement which separates the dirt from the air. Often the dirty air inlet will have a beater bar or brush roller which is rotated to agitate the floor covering and loosen the dirt so as to increase the amount of dirt and dust which is drawn into the cleaner via the dirty air inlet.
Robotic floor cleaning devices are known. Such devices can move around on a work surface according to a predetermined pattern or by random changes of direction of movement, cleaning the surface of dust and dirt as it travels. The device can be battery powered and will have a chassis, wheels to support the chassis, separate drive motors to drive the wheels, a suction fan, and a rotatable beater bar or brush roller. It is recognised that the rotating brush roller or beater bar can cause problems when there are loose carpet tassels or fringes and the like present on the floor because the tassels can become entangled with the brush roller or beater bar.
International Patent Application WO 97/40734 attempts to tackle this problem in an autonomous device having a brush roller. The device is programmed with a sequence so that, if there is an indication of the brush roller becoming jammed (which will often be due to the presence of a fringe or tassels), the brush roller motor is disconnected whereafter the motor is again transitorily switched on but in the opposite direction. This makes it possible for the carpet fringes to be unwound from the brush roller and fed out. When this reverse rotation step has been completed the brush roller motor is again stopped and thereafter the drive is reconnected so that the brush roller is rotated in the original direction of rotation.
It is stated in the aforementioned published application that in the normal case this would be sufficient for the release of the brush roller so that the normal cleaning function can be re-established. It is also stated that, should this not be the case, the disentanglement procedure will be repeated.
In the published application the drive current of the brush roller motor is sensed and compared with a limit value in order to detect whether the brush roller is jammed. If the limit is exceeded, the current driving the brush roller motor is first stopped and then applied in the opposite direction in order to rotate the brush roller in the reverse direction. When normal cleaning is to be resumed the motor current is again applied in the initial direction.
International Patent Application WO 99/28800 shows a robotic cleaner with a rotary brush where the brush is freed by cutting the power supply to the motor and performing a series of manoeuvres.
In both of these applications, manual intervention is required if the cleaner cannot successfully free the brush roller.
It is an object of the present invention to provide a robotic floor cleaning device which can more successfully cope with its environment.
According to the present invention there is provided a robotic floor cleaning device comprising a chassis, motor-driven wheels supporting the chassis, a motor-driven suction fan, a dirty air inlet, a motor-driven rotatable agitator at the dirty air inlet for agitating the surface to be cleaned, a control system for navigating the device around a room and for distributing power to the motor-driven wheels and to the agitator, the control system being arranged to operate the device in a first mode of operation in which power is supplied to the motor-driven wheels to move the device in a forward direction and power is supplied to the agitator, the control system further being arranged to detect when the agitator has jammed and, in the event of a jam, to attempt to clear the jam and after successfully clearing the jam to proceed in a second mode of operation.
In the second mode of operation, the control system can be arranged to turn off the agitator or to navigate the cleaning device around the position where the jam occurred. The cleaning device can remain in the second mode of operation for a preset distance or time or until some other condition is met.
By operating in a second mode of operation, the agitator is less likely to become jammed a second time, thus saving time and power which would otherwise be expended in carrying out the further attempts to clear the jam. Some environments where the cleaning device is operated may have obstacles such as rugs with tassels which cannot be negotiated with the agitator in use. By providing the second mode of operation, the cleaning device is better able to cope with these environments without manual intervention.
Preferably the cleaning device attempts to clear the jam by disconnecting the power to the agitator and then reversing the rotation of the motor-driven wheels of the device to move the device in a reverse direction.
A further aspect of the invention provides a robotic floor cleaning device comprising a chassis, motor-driven wheels supporting the chassis, a motor-driven suction fan, a dirty air inlet, a motor-driven rotatable agitator at the dirty air inlet for agitating the surface to be cleaned, a control system for navigating the device around a room and for distributing power to the motor-driven wheels and to the agitator, the control system being arranged to operate the device in a first mode of operation in which power is supplied to the motor-driven wheels to move the device in a forward direction and power is supplied to the agitator, to detect when the agitator has jammed and, in the event of a jam, to attempt to clear the jam and to store information representative of the location of the jam, the control system further being arranged to subsequently navigate the cleaning device around the room and to operate the device in a second mode of operation when the device approaches the location of a previous jam.
In the second mode of operation, the control system can turn off the agitator, navigate the cleaning device around the location where the agitator jammed or navigate the device so that the location at which the agitator became jammed is not overrun except from a direction different from the direction of first approach thereto.
By operating in a second mode of operation the before the jam location is reached, the agitator is less likely to become jammed a further time, thus saving time and power which would otherwise be expended in carrying out the further attempts to clear the jam.
Further preferable and advantageous features of the invention are set out in the subsidiary claims.